The fundamental functionality of a fluid flow control valve is the regulation of the flow of fluid between its input and output ports. In micro-fluid flow control systems requiring precise regulation of the rate of fluid flow in extremely reduced volume fluid flow applications, the micro-valve assemblies that have been customarily employed are of two basic types. The first, diagrammatically illustrated in FIG. 1, employs a needle valve 1, having a conically tapered nose portion 2, which is controllably translated through a relatively long stroke along the axis 3 of a fluid bore 4. Because of the length of the stroke and the gradual taper of the needle valve, it is possible to very precisely adjust the effective area of an annular region defined between the surface of the conically tapered nose of the needle valve and the fluid bore, and thereby provide precise control of the fluid flow rate between and input port 5 and an exit port 6, which are in fluid communication with opposite ends of the bore 4. Now, although such a needle valve assembly allows the fluid flow rate to be very finely adjusted, the flow rate is non-linear over the range of displacement of the valve, as shown by fluid flow rate curve II in FIG. 2.
A second type of micro-valve assembly, diagrammatically illustrated in FIG. 3, employs a poppet 7 that is translated over a very short stroke along an axis 8 relative to a valve seat 9, which surrounds a fluid bore 10 the rate of flow through which is to be controlled. Advantageously, as shown at curve IV in FIG. 4, the poppet type of micro-valve assembly of FIG. 3 is capable of providing a very linear fluid flow rate over a prescribed range of separation D.sub.79 of the poppet 7 from the valve seat 9. Unfortunately, because the range of translation or stroke of the poppet relative to the valve seat that provides the linear fluid flow rate is extremely small (e.g. on the order of twenty-five thousandths of an inch), adjusting and setting the fluid flow rate is a very difficult and imprecise task. Indeed, the short stroke encountered in a conventional mechanical translation mechanism, which conventionally involves directly rotating a threaded valve stem to which the poppet is attached (as by way of a cap or sleeve solid with the valve stem), does not provide for a smooth and fine adjustment of the translation of the poppet 7 relative to the valve seat within such a narrow range of opening.